The sexy singer - who took time off to marry husband Kevin Federline and have their baby son, Sean Preston - is said to be losing clumps of her luscious locks.
Britney has even reportedly started wearing huge hats to cover her thinning tresses.
A source told Britain's Daily Star newspaper: 'It looks like the poor poppet is suffering from stress-related alopecia.'
The singer - who gained 50lbs during pregnancy - has been feeling the strain because she has been worrying about her husband's partying, while caring for their baby, and is also concerned about getting in shape for her comeback.
The source added: 'The real cause of her thinning hair is her constant fretting about getting slim and developing a new look for her return to pop.'
Meanwhile, Britney has reportedly taken up yoga to shift her baby weight.
The pop beauty has lost most of her pregnancy weight but is desperate to shift the remaining extra pounds.
The 'Toxic' singer has also ditched the junk food which she was repeatedly spotted gorging on while expecting.